At present, mobile terminal products available in the market, such as a mobile phone and a data card, are basically capable of performing charging and discharging management for only one battery at the same time. However, the capacity of one battery is limited, which results in a limited time for supplying power for a mobile terminal product. When the capacity of the battery of the mobile terminal product is exhausted, a user of the mobile terminal product must charge the battery. A battery is charged in a following mode: powering off a mobile terminal product, taking off the battery, and putting it on a dedicated charging device for charging; or, using a USB connection wire or the like to connect a charging interface of a handheld terminal product to a device capable of charging a battery, thereby charging the battery. If the battery is charged in the first mode, the user must power off the mobile terminal product and the user cannot use the mobile terminal product during such a period. If the battery is charged in the second mode, the location where the user uses the mobile terminal product is limited to a small area. That is, when the user charges the mobile terminal product, the mobile terminal product must be powered off or the location where the user uses the mobile terminal product is limited to a small area.